Integrated circuits in optical receivers

ABSTRACT

A circuit may include a photodiode configured to receive an optical signal and convert the optical signal to a current signal. The circuit may also include a transimpedance amplifier coupled to the photodiode and configured to convert the current signal to a voltage signal. The circuit may also include an equalizer coupled to the transimpedance amplifier and configured to equalize the voltage signal to at least partially compensate for a loss of a high frequency component of the optical signal. The equalizer and the transimpedance amplifier may be housed within a single integrated circuit.

FIELD

The embodiments discussed herein are related to integrated circuits foroptical receivers.

BACKGROUND

Optical systems use optical signals traveling through optical channels,such as optical fibers, to transmit data. As data rates of the opticalsignals increase, the frequency response of the optical signals may bealtered. In particular, high frequency components of optical signals maybe subject to more loss than low frequency components of opticalsignals. The loss of the high frequency components of optical signalsmay be caused by the optical fibers, the transmitters that generate theoptical signals, among other components and factors. Loss of the highfrequency components of optical signals within optical systems mayreduce the ability of the optical systems to transmit data at higherspeeds within proper error tolerances and may lead to data transmissionfailures within the optical systems.

The subject matter claimed herein is not limited to embodiments thatsolve any disadvantages or that operate only in environments such asthose described above. Rather, this background is only provided toillustrate one exemplary technology area where some embodimentsdescribed herein may be practiced.

SUMMARY

Some example embodiments generally relate to integrated circuits.

In an embodiment, a circuit may include a photodiode configured toreceive an optical signal and convert the optical signal to a currentsignal. The circuit may also include a transimpedance amplifier coupledto the photodiode and configured to convert the current signal to avoltage signal. The circuit may also include an equalizer coupled to thetransimpedance amplifier and configured to equalize the voltage signalto at least partially compensate for a loss of a high frequencycomponent of the optical signal. The equalizer and the transimpedanceamplifier may be housed within a single integrated circuit.

In an embodiment, an integrated circuit may include an input stageconfigured to receive a current signal from a photodiode and convert itto a voltage signal using a transimpedance amplifier. The current signalmay represent an optical signal received by the photodiode. Theintegrated circuit may further include an equalizer coupled to thetransimpedance amplifier and configured to equalize the voltage signalto at least partially compensate for a loss of a high frequencycomponent of the optical signal. The integrated circuit may also includea driver configured to drive the equalized voltage signal from theintegrated circuit to another integrated circuit.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential characteristics of the claimed subject matter, nor is itintended to be used as an aid in determining the scope of the claimedsubject matter.

Additional features and advantages of the invention will be set forth inthe description that follows or may be learned by the practice of theinvention. The features and advantages of the invention may be realizedand obtained by means of the instruments and combinations particularlypointed out in the appended claims. These and other features of thepresent invention will become more fully apparent from the followingdescription and appended claims, or may be learned by the practice ofthe invention as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more particular description of the invention will be rendered byreference to embodiments thereof, which are illustrated in the appendeddrawings. It is appreciated that these drawings depict only someembodiments of the invention and are therefore not to be consideredlimiting of its scope. The invention will be described and explainedwith additional specificity and detail through the use of theaccompanying drawings in which:

FIG. 1A is a block diagram of an example optical system that includes anintegrated circuit;

FIG. 1B illustrates a graph of a frequency response of a voltageelectrical signal within the optical system of FIG. 1A;

FIG. 2 is a block diagram of an example receiver that includes anintegrated circuit;

FIG. 3 is a block diagram of an example equalizer;

FIG. 4A illustrates an example static equalizer;

FIG. 4B illustrates an example adjustable equalizer;

FIG. 5 is a block diagram of another example receiver that includes anintegrated circuit; and

FIG. 6 is a perspective view of an example optoelectronic module thatmay include an integrated circuit.

DETAILED DESCRIPTION

Some embodiments described herein may include an integrated circuit. Theintegrated circuit may include a transimpedance amplifier (TIA) and anequalizer circuit and may be part of an optical receiver circuitconfigured to convert an optical signal received over an optical channelinto an electrical signal.

The TIA within the integrated circuit may be configured to convert acurrent signal generated by a photodiode based on a received opticalsignal into a voltage signal. The equalizer circuit may be configured toequalize the voltage signal to at least partially compensate for a lossof high frequency components of the received optical signal.

By integrating the TIA and the equalizer into a single integratedcircuit, a driver coupled to the TIA and the equalizer circuit fordriving the equalized voltage signal to other circuits and/or integratedcircuits, such as a clock and data recovery circuit, may be non-linear.Allowing the driver to be non-linear may reduce the power used by thedriver and thus the optical receiver circuit. Additionally oralternately, by equalizing the voltage signal generated by the TIAbefore driving the voltage signal to another circuit and/or integratedcircuit allows the TIA to be decoupled from the other circuit and/orintegrated circuit. Decoupling the TIA from another circuit and/orintegrated circuit may allow for higher levels of interference betweenthe TIA and the another circuit and/or integrated circuit than would beallowed if the voltage signal generated by the TIA was not equalizedbefore sending the voltage signal to the another circuit and/orintegrated circuit.

FIG. 1A is a block diagram of an example optical system 100 thatincludes an integrated circuit 124, arranged in accordance with at leastsome embodiments described herein. The optical system 100 may include,but is not limited to, a transmitter 110, an optical channel 112, areceiver 120 that includes the integrated circuit 124, and a clock anddata recovery circuit (CDR circuit) 130.

The transmitter 110 may be configured to generate an optical signal froman electrical signal and to transmit the optical signal through theoptical channel 112. In some embodiments, the transmitter 110 mayinclude an equalizer that may be configured to equalize the electricalsignal before the electrical signal is converted into the opticalsignal. In these and other embodiments, the transmitter 110 may equalizethe electrical signal to assist in compensating for degradation of theoptical signal as it travels through the optical channel 112.Alternately or additionally, the transmitter 110 may equalize theelectrical signal to assist in compensating for degradation of theoptical signal due to the transmitter 110 operating at a slower ratethan the data rate of the electrical and optical signals.

The optical channel 112 may be any channel configured to carry anoptical signal. For example, the optical channel 112 may be an opticalfiber, such as a multi-mode optical fiber, or some other type of opticalfiber. The properties of the optical channel 112 may result indegradation of the optical signal as the optical signal traverses theoptical channel 112. In some embodiments, the optical channel 112 mayaffect the higher frequency components of the optical signal more thanthe lower frequency components of the optical signal. In these and otherembodiments, the optical channel 112 may degrade the higher frequencycomponents more than the lower frequency components.

The receiver 120 may be coupled to the optical channel 112 and may beconfigured to receive the optical signal. The receiver 120 may also beconfigured to convert the optical signal to an electrical signal and totransmit the electrical signal to the CDR circuit 130. In particular,the receiver 120 may be configured to convert the optical signal to acurrent electrical signal and then convert the current electrical signalto a voltage signal that is transmitted to the CDR circuit 130.

The receiver 120 may convert the optical signal to the currentelectrical signal using a photodiode or some other optical to electricalconverter. After converting the optical signal to the current electricalsignal, the integrated circuit 124 may convert the current electricalsignal to a voltage electrical signal. The integrated circuit 124 mayalso equalize the voltage electrical signal to at least partiallycompensate for the degradation of higher frequency components of theoptical signal that occur due to limitations, defects, or other aspectsof the transmitter 110 and/or the optical channel 112. After theintegrated circuit 124 converts the optical signal into a voltageelectrical signal and equalizes the voltage electrical signal, theintegrated circuit 124 may send the equalized voltage electrical signalto the CDR circuit 130.

The integrated circuit 124 may house circuitry to both convert a currentelectrical signal into a voltage electrical signal and to equalize thevoltage electrical signal. By equalizing the voltage electrical signalbefore sending the voltage electrical signal to the CDR circuit 130, thepower used by the optical system 100 may be reduced as compared tooptical systems that equalize voltage electrical signals in a CDRcircuit or some other circuit besides the circuit that converts thecurrent electrical signal to the voltage electrical signal. The powerused by the optical system 100 may be reduced because the voltageelectrical signal may be transmitted to the CDR circuit 130 from thereceiver 120 using non-linear drivers instead of linear drivers.Non-linear drivers may be used because the non-linear effects thataffected the optical signal during creation and/or transmission of theoptical signal have already been accounted for by the integrated circuit124 by equalizing the voltage electrical signal. Alternately oradditionally, equalizing the voltage electrical signal allows thereceiver 120 to be decoupled from the CDR circuit 130. Alternately oradditionally, equalizing the voltage electrical signal may allow forhigher levels of interference between the receiver 120 and the CDRcircuit 130 without causing unacceptable loss of the equalized voltageelectrical signal transmitted to the CDR circuit 130 from the receiver120.

Modifications, additions, or omissions may be made to the optical system100 without departing from the scope of the present disclosure. Forexample, the receiver 120 may send the equalized voltage electricalsignal to another circuit other than the CDR circuit 130.

FIG. 1B illustrates a graph 150 of a frequency response of a voltageelectrical signal within the optical system 100 of FIG. 1A, arranged inaccordance with at least some embodiments described herein. The graph150 has an x-axis that represents a frequency of various frequencycomponents of a voltage electrical signal. The y-axis of the graph 150represents a magnitude of the frequency components of the voltageelectrical signal. The graph contains a line 160 and a dashed line 170.

The line 160 indicates a magnitude of different frequency components ofthe voltage electrical signal after the voltage electrical signal isderived from an optical signal that passes through the optical system100. As illustrated by the line 160, the magnitudes of the higherfrequency components of the voltage electrical signal are attenuatedmore than the magnitudes of the lower frequency components of thevoltage electrical signal. Examples of higher frequency components thatmay have reduced magnitudes include frequency components havingfrequencies above a few GHz.

The dashed line 170 indicates a magnitude of different frequencycomponents of the voltage electrical signal after the voltage electricalsignal is derived from an optical signal that passes through the opticalsystem 100 and is equalized by the integrated circuit 124. Asillustrated by the dashed line 170, the magnitudes of the higherfrequency components of the voltage electrical signal are increased ascompared to the magnitudes of the higher frequency components of thevoltage electrical signal without equalization.

FIG. 2 is a block diagram of an example receiver 200 that includes anintegrated circuit 210, arranged in accordance with at least someembodiments described herein. The receiver 200 may include, but is notlimited to, a photodiode 214 coupled to the integrated circuit 210. Theintegrated circuit 210 may include a transimpedance amplifier (TIA) 220,an equalizer 230, a driver 240, an input port 215, a communication port216, and an output port 218.

FIG. 2 further illustrates an optical fiber 212 adjacent to thephotodiode 214. The optical fiber 212 may be any type of optical fiber,such as a multi-mode fiber, that is configured to transmit an opticalsignal. The photodiode 214 may be configured to receive an opticalsignal from the optical fiber 212. The photodiode 214 may also beconfigured to convert the received optical signal into a currentelectrical signal and to send the current electrical signal to the inputport 215 of the integrated circuit 210.

The TIA 220 may be configured to receive the current electrical signalfrom the input port 215 and to convert the current electrical signalinto a voltage electrical signal. In some embodiments, the TIA 220 mayalso amplify the voltage electrical signal. In some embodiments, the TIA220 may have a linear response or an approximate linear response. Thus,the TIA 220 may have no or a marginally different effect on differentfrequency components of the voltage electrical signal. Thus, differencesin magnitudes between frequency components may be marginally maintained.The TIA 220 may send the voltage electrical signal to the equalizer 230.

The equalizer 230 may be configured to equalize the voltage electricalsignal. To equalize the voltage electrical signal, the equalizer 230 mayadjust the magnitude of certain frequency components of the voltageelectrical signal to reduce differences between magnitudes of frequencycomponents of the voltage electrical signal. For example, if higherfrequency components of the voltage electrical signal had lowermagnitudes than lower frequency components, the equalizer 230 may reducethe magnitude of lower frequency components, increase the magnitude ofhigher frequency components, or some combination thereof, to reduce thedifferences between the magnitudes of the frequency components.Equalizing the voltage electrical signal may reduce intersymbolinterference of a data signal transmitted on the optical signal throughthe optical fiber 212. Reducing intersymbol interference may allow forbetter recovery of the data signal. The equalizer 230 may send theequalized voltage electrical signal to the driver 240.

In some embodiments, the equalizer 230 may be a linear equalizer, suchas a continuous time linear equalizer or a linear feed forwardequalizer. Alternately or additionally, the equalizer 230 may be astatic equalizer, an adjustable equalizer, or a combination thereof. Astatic equalizer may adjust the magnitude of one or more frequencycomponents of a signal in a consistent manner. An adjustable equalizermay adjust the magnitude of one or more frequency components of a signalbased on a setting within the adjustable equalizer that may be adjustedbased on an input. For example, the communication port 216 may beconfigured to receive an indication from an outside source of thefrequency components of a voltage electrical signal whose magnitudes areaffected and/or how much the magnitudes are affected. Based on theindication from the outside source, the equalizer 230 may adjust theequalization of the voltage electrical signal. The communication port216 may be any type of communication port, such as a serial port or aparallel port. When the communication port 216 is a serial port, theintegrated circuit 210 may interface with an outside source using anyone of numerous serial communication protocols, such as, but not limitedto, I²C, SPI, serial ATA, FireWire, PCI, PCI express, among others. Whenthe communication port 216 is a parallel port, the integrated circuit210 may interface with an outside source using any one of numerousparallel communication protocols, such as, but not limited to ISA,parallel ATA, SCSI, among others.

The driver 240 may receive the equalized voltage electrical signal fromthe equalizer 230 and driver the equalized voltage electrical signal outthe output port 218 to another circuit, such as an another integratedcircuit. For example, the driver 240 may drive the equalized voltageelectrical signal to a CDR circuit. In some embodiments, the driver 240may have a non-linear response. The driver 240 having a non-linearresponse as compared to a linear response may reduce the powerconsumption of the driver 240 and subsequently the power consumption ofthe integrated circuit 210. The driver 240 may have a non-linearresponse because the voltage electrical signal is equalized by theequalizer 230 before being driven by the driver 240. In circumstanceswhere a receiver, similar to the receiver 200, does not have anequalizer, a driver of the receiver may have a linear or substantiallylinear response to minimize changes to a voltage electrical signal; tothereby decrease errors in a data signal extracted from the voltageelectrical signal.

Modifications, additions, or omissions may be made to the receiver 200without departing from the scope of the present disclosure. For example,the receiver 200 may include an optical to electrical converter besidesa photodiode. As another example, the integrated circuit 210 may notinclude the driver 240. In these and other embodiments, the TIA 220 andthe equalizer 230 may form the integrated circuit 210 and the driver 240may be a separate component. As another example, in some embodiments,the integrated circuit 230 may not include the communication port 216.In these and other embodiments, the equalizer 230 may be a staticequalizer.

FIG. 3 is a block diagram of an example equalizer 300, arranged inaccordance with at least some embodiments described herein. Theequalizer 300 may include, but is not limited to, a static portion andan adjustable portion. The static portion may include a static equalizerunit 310 and the adjustable portion may include an adjustable equalizerunit 320. The equalizer 300 may be configured to receive a signal andprovide equalization among frequency components of the signal.

The static equalizer unit 310 may be configured to provide constantequalization of a signal received by the equalizer 300. Providingconstant equalization may include the static equalizer unit 310adjusting magnitudes of set frequency components of the signal by apredetermined amount. For example, the static equalizer unit 310 mayincrease the magnitude of frequency components of a signal above 5 GHzby 20 dB. In some embodiments, the static equalizer unit 310 may be adigital equalizer or an analog equalizer.

The adjustable equalizer unit 320 may be configured to provideadjustable equalization of a signal received by the equalizer 300.Providing adjustable equalization may include the adjustable equalizerunit 320 adjusting the magnitudes of set frequency components of thesignal by an adjustable amount, adjusting the magnitude of adjustablefrequency components of the signal by a set amount, or some combinationthereof. For example, the adjustable equalizer unit 320 may increase amagnitude of frequency components of a signal above 5 GHz by 20 dB andthen may be adjusted to increase the magnitude of the frequencycomponents of the signal above 5 GHz by 10 dB. As another example, theadjustable equalizer unit 320 may increase a magnitude of frequencycomponents of a signal above 5 GHz by 20 dB and then may be adjusted toincrease the magnitude of the frequency components of the signal above 7GHz by 20 dB. In some embodiments, the adjustable equalizer unit 320 maybe a digital equalizer or an analog equalizer. The adjustable equalizerunit 320 may be adjusted based on an input received through acommunication port 322 in the equalizer 300.

The equalizer 300 may be incorporated into a single integrated circuitwith other components, such as a TIA. For example, the equalizer 300 maybe used in place of the equalizer 230 of FIG. 2. Alternately oradditionally, the equalizer 300 may be part of the IC 124 of FIG. 1A.

Modifications, additions, or omissions may be made to the equalizer 300without departing from the scope of the present disclosure. For example,the equalizer 300 may include multiple static equalizers or multipleadjustable equalizers. Alternately or additionally, the equalizer 300may not include the static equalizer unit 310 or the adjustableequalizer unit 320.

FIG. 4A illustrates an example static equalizer 400A, arranged inaccordance with at least some embodiments described herein. The staticequalizer 400A may include, but is not limited to, resistors 402 and 404and capacitor 406. The resistors 402 and 404 may form a resistivedivider, with the resistor 402 coupled to an input and an output of thestatic equalizer 400A and the resistor 404 coupled between the outputand ground. The capacitor 406 may be coupled across the resistor 402between the input and the output. The static equalizer 400A may operateas a resistive divider of lower frequency components of a signal therebyreducing the magnitude of lower frequency components. Higher frequencycomponents of the static equalizer 400A may pass by the resistor dividerby way of the capacitor 406. The static equalizer 400A may thus equalizea signal by reducing a magnitude of lower frequency components to besimilar in magnitude to higher frequency components. The amount ofreduction in magnitude and the higher frequencies that may pass withouthaving a reduction in magnitude may be selected based on the values ofthe resistors 402 and 404 and the capacitor 406. Modifications,additions, or omissions may be made to the static equalizer 400A withoutdeparting from the scope of the present disclosure. For example,additional active and/or passive circuit elements may be included in thestatic equalizer 400A.

FIG. 4B illustrates an example adjustable equalizer 400B, arranged inaccordance with at least some embodiments described herein. Theadjustable equalizer 400B may be configured to equalize a signal basedon a selected value for one or more adjustable values.

The adjustable equalizer 400B may include, but is not limited to,adjustable gain blocks 410, 412, and 414, delay blocks 420 and 422, anda summer 430. The delay blocks 420 and 422 may have the same delay orvarying delays. The adjustable gain blocks 410, 412, and 414 may each beadjusted to increase and/or decrease a magnitude of a signal or adelayed portion of the signal. For example, the adjustable gain block410 may have a gain of ½ and thus decrease a magnitude of a signal andthe adjustable gain block 412 may have a gain of 2 and thus increase amagnitude of the signal or a delayed portion of the signal.

A signal at an input of the adjustable equalizer 400B may be sent to thegain block 410 and the delay block 420. The gain block 410 may adjust amagnitude of the signal and may send the adjusted signal to the summer430. The delay block 420 may delay the signal. A magnitude of thedelayed signal may be adjusted by the gain block 412. The adjusteddelayed signal from the gain block 412 may be sent to the summer 430.The delay block 422 may further delay the delayed signal and may sendthe twice-delayed signal to the gain block 414. The gain block 414 mayadjust a magnitude of the twice-delayed signal and may send the adjustedtwice-delayed signal to the summer 430. The summer 430 may sum theadjusted signal, the adjusted delayed signal, and the adjustedtwice-delayed signal and may output the result on an output of theadjustable equalizer 400B. The adjustable equalizer 400B may equalize asignal by increasing a magnitude of higher frequency components of asignal to be more similar to a magnitude of lower frequency components.Modifications, additions, or omissions may be made to the adjustableequalizer 400B without departing from the scope of the presentdisclosure. For example, the adjustable equalizer 400B may be configuredwith an additional delay block and gain block. Alternately oradditionally, the adjustable equalizer 400B may be configured with afeedback loop and a gain block.

FIG. 5 is a block diagram of another example receiver 500 that includesan integrated circuit 510, arranged in accordance with at least someembodiments described herein. The receiver 500 may include, but is notlimited to, a photodiode 514 coupled to the integrated circuit 510. Theintegrated circuit 510 may include a TIA 520, an equalizer 530, a driver540, an input port 515, a communication port 516, and an output port518.

FIG. 5 further illustrates an optical fiber 512 adjacent to thephotodiode 514. The optical fiber 512 may be any type of optical fiber,such as a multi-mode fiber, that is configured to transmit an opticalsignal. The photodiode 514 may be configured to receive an opticalsignal from the optical fiber 512. The photodiode 514 may also beconfigured to convert the optical signal into a current electricalsignal and to send the current electrical signal to the input port 515of the integrated circuit 510.

The TIA 520 may be configured to receive the current electrical signalfrom the input port 515 and to convert the current electrical signalinto a pair of differential voltage electrical signals. The TIA 520 mayinclude a first amplifier 522 and a first resistor 521 that may beconfigured to convert the current electrical signal from the photodiode514 into a first voltage signal of the pair of differential voltageelectrical signals. The TIA 520 may also include a capacitor 525, asecond amplifier 523, and a second resistor 524 that may be configuredto generate a second voltage signal of the pair of differential voltageelectrical signals based on the current signal and/or the first voltagesignal. The first and second voltage signals may be amplified by anamplifier 528 and sent to the equalizer 530.

In some embodiments, the TIA 520 may have a linear response or anapproximate linear response. Thus, the TIA 520 may have no or amarginally different effect on different frequency components of thepair of differential voltage electrical signals. Thus, differences inmagnitudes between frequency components may be marginally maintained.

The equalizer 530 may be configured to equalize the pair of differentialvoltage electrical signals. The equalizer 500 may include, but is notlimited to, a static portion and an adjustable portion. The staticportion may include a static equalizer unit 534 and the adjustableportion may include an adjustable equalizer unit 532. The staticequalizer unit 534 may be configured to equalize the pair ofdifferential voltage electrical signals by adjusting a magnitude of setfrequency components of the pair of differential voltage electricalsignals by a predetermined amount. The static equalizer unit 534 maydecrease or increase the magnitude of higher or lower frequencycomponents of the pair of differential voltage electrical signals toequalize the pair of differential voltage electrical signals.

The adjustable equalizer unit 532 may be configured to provideadjustable equalization of the pair of differential voltage electricalsignals. In some embodiments, an amount of equalization provided by theadjustable equalizer unit 532 may be determined based on an inputreceived through the communication port 516. In some embodiments, theadjustable equalizer unit 532 may be configured to further reduce and/orincrease high or low frequency components of the pair of differentialvoltage electrical signals based on the equalization performed by thestatic equalizer unit 534. Alternately or additionally, the adjustableequalizer unit 532 may be configured to reduce a magnitude of afrequency component whose magnitude is increased by the static equalizerunit 534 or increase a magnitude of a frequency component whosemagnitude is decreased by the static equalizer unit 534. The adjustableequalizer unit 532 may be used to provide finer tuned equalization ofthe pair of differential voltage electrical signals. In someembodiments, the static and the adjustable equalizer units 534 and 532may be linear equalizers. Alternately or additionally, the static andthe adjustable equalizer units 534 and 532 may be digital equalizers,analog equalizers, or some combination thereof. The equalizer 530 maysend the equalized pair of differential voltage electrical signals tothe driver 540.

The driver 540 may receive the equalized pair of differential voltageelectrical signals from the equalizer 530 and driver the equalized pairof differential voltage electrical signals out the output port 218 toanother circuit, such as an another integrated circuit. For example, thedriver 540 may drive the equalized pair of differential voltageelectrical signals to a CDR circuit. In some embodiments, the driver 540may have a non-linear response.

Modifications, additions, or omissions may be made to the receiver 500without departing from the scope of the present disclosure. For example,the integrated circuit 510 may not include the driver 540. In these andother embodiments, the TIA 520 and the equalizer 530 may form theintegrated circuit 510 and the driver 540 may be a separate component.In some embodiments, the TIA 520 may include additional active and/orpassive circuit elements. In some embodiments, the equalizer 530 mayinclude additional static or adjustable equalizer units or may notinclude either the static equalizer unit 534 or the adjustable equalizerunit 532.

FIG. 6 is a perspective view of an example optoelectronic module 600(hereinafter “module 600”) that may include an integrated circuit 620,arranged in accordance with at least some embodiments described herein.The module 600 may be configured for use in transmitting and receivingoptical signals in connection with a host device (not shown).

As illustrated, the module 600 may include, but is not limited to, abottom housing 602; a receive port 604 and a transmit port 606, bothdefined in the bottom housing 602; a PCB 608 positioned within thebottom housing 602, the PCB 608 having the integrated circuit 620 and asecond integrated circuit 622 positioned hereon; and a receiver opticalsubassembly (ROSA) 610 and a transmitter optical subassembly (TOSA) 612also positioned within the bottom housing 602. An edge connector 614 maybe located on an end of the PCB 608 to enable the module 600 toelectrically interface with the host device. As such, the PCB 608facilitates electrical communication between the host device and theROSA 610 and TOSA 612.

The module 600 may be configured for optical signal transmission andreception at a variety of data rates including, but not limited to, 1Gb/s, 10 Gb/s, 20 Gb/s, 40 Gb/s, 100 Gb/s, or higher. Furthermore, themodule 600 may be configured for optical signal transmission andreception at various distinct wavelengths using wavelength divisionmultiplexing (WDM) using one of various WDM schemes, such as Coarse WDM,Dense WDM, or Light WDM. Furthermore, the module 600 may be configuredto support various communication protocols including, but not limitedto, Fibre Channel and High Speed Ethernet. In addition, althoughillustrated in a particular form factor in FIG. 6, more generally, themodule 600 may be configured in any of a variety of different formfactors including, but not limited to, the Small Form-factor Pluggable(SFP), the enhanced Small Form-factor Pluggable (SFP+), the 10 GigabitSmall Form Factor Pluggable (XFP), the C Form-factor Pluggable (CFP) andthe Quad Small Form-factor Pluggable (QSFP) multi-source agreements(MSAs).

The ROSA 610 may house one or more optical receivers, such asphotodiodes, that are electrically coupled to an electrical interface616. The one or more optical receivers may be configured to convertoptical signals received through the receive port 604 into correspondingcurrent electrical signals that are relayed to the integrated circuit620 through the electrical interface 616 and the PCB 608. The TOSA 612may house one or more optical transmitters, such as lasers, that areelectrically coupled to another electrical interface 618. The one ormore optical transmitters may be configured to convert electricalsignals received from a host device by way of the PCB 608 and theelectrical interface 618 into corresponding optical signals that aretransmitted through the transmit port 606.

The integrated circuit 620, which may be similar to and/or correspond tothe integrated circuits 124, 210, or 510 of FIG. 1, 2, or 5respectively, may be configured to convert the current electricalsignals to voltage electrical signals and to equalize the voltageelectrical signals. The integrated circuit 620 may drive the equalizedvoltage electrical signals to the second integrated circuit 622. In someembodiments, the second integrated circuit may be a CDR circuit. In someembodiments, an integrated circuit, such as the integrated circuits 124,210, or 510 of FIG. 1, 2, or 5 respectively may be incorporated into theROSA 610 and may be used to convert current electrical signals toequalized voltage electrical signals. Modifications, additions, oromissions may be made to the module 600 without departing from the scopeof the present disclosure.

The module 600 illustrated in FIG. 6 is one architecture in whichembodiments of the present disclosure may be employed. This specificarchitecture is only one of countless architectures in which embodimentsmay be employed. The scope of the present disclosure is not intended tobe limited to any particular architecture or environment.

All examples and conditional language recited herein are intended forpedagogical objects to aid the reader in understanding the invention andthe concepts contributed by the inventor to furthering the art, and areto be construed as being without limitation to such specifically recitedexamples and conditions. Although embodiments of the present inventionshave been described in detail, it should be understood that the variouschanges, substitutions, and alterations could be made hereto withoutdeparting from the spirit and scope of the invention.

What is claimed is:
 1. A circuit comprising: a photodiode configured toreceive an optical signal and convert the optical signal to a currentsignal; a transimpedance amplifier coupled to the photodiode andconfigured to convert the current signal to a voltage signal; and anequalizer coupled to the transimpedance amplifier and configured toequalize the voltage signal to at least partially compensate for a lossof a high frequency component of the optical signal, the equalizer andthe transimpedance amplifier being housed within a single integratedcircuit.
 2. The circuit of claim 1, wherein the equalizer comprises alinear equalizer.
 3. The circuit of claim 1, wherein the equalizercomprises a linear feed forward equalizer or a continuous time linearequalizer.
 4. The circuit of claim 1, wherein the equalizer comprises ananalog equalizer.
 5. The circuit of claim 1, wherein the equalizercomprises a digital equalizer.
 6. The circuit of claim 5, wherein theequalizer further comprises an analog equalizer.
 7. The circuit of claim5, wherein the digital equalizer is configured to allow for adjustmentof equalization performed by the digital equalizer.
 8. The circuit ofclaim 1, further comprising a driver coupled to the equalizer, thedriver configured to drive the equalized voltage signal and being housedwithin the single integrated circuit.
 9. The circuit of claim 8, whereinthe driver comprises a non-linear driver.
 10. The circuit of claim 8,wherein the driver is configured to drive the equalized voltage signalto a clock and data recovery circuit in another integrated circuitseparate from the single integrated circuit.
 11. The circuit of claim 1,wherein the voltage signal comprises a pair of differential voltagesignals.
 12. An integrated circuit comprising: an input configured toreceive a current signal from a photodiode, the current signalrepresentative of an optical signal received by the photodiode; atransimpedance amplifier coupled to the input and configured to convertthe current signal to a voltage signal; an equalizer coupled to thetransimpedance amplifier and configured to equalize the voltage signalto at least partially compensate for a loss of a high frequencycomponent of the optical signal; and a driver configured to drive theequalized voltage signal from the integrated circuit to anotherintegrated circuit.
 13. The integrated circuit of claim 12, wherein theequalizer comprises: a static portion configured to provide constantequalization of the voltage signal; and an adjustable portion configuredto provide adjustable equalization of the voltage signal.
 14. Theintegrated circuit of claim 13, wherein the static portion of theequalizer comprises an analog equalizer.
 15. The integrated circuit ofclaim 13, wherein the adjustable portion of the equalizer comprises adigital equalizer.
 16. The integrated circuit of claim 12, wherein thedriver comprises a non-linear driver.
 17. The integrated circuit of 16,wherein the transimpedance amplifier has a substantially linearfrequency response.
 18. The integrated circuit of claim 12, wherein theoptical signal is generated by a transmitter, the transmitter comprisinga transmitting equalizer.
 19. The integrated circuit of claim 12,wherein the voltage signal comprises a pair of differential voltagesignals.